Over medium-high heat, heat 2 tbsp. water in the cooker. Cook the onions, stirring frequently, for 2 minutes. Add the broth and stir well to scrape up any browned bits sticking to the bottom of the cooker. Add the lentils, bulgur, and red pepper flakes, if using.

Lock the lid in place. Over high heat, bring to high pressure. Lower the heat just enough to maintain high pressure and cook for 10 minutes. Quick-release the pressure. Remove the lid, tilting it away from you to allow any excess steam to escape.

Stir in the garlic, tomatoes, mint, and salt. Simmer until the garlic loses its raw taste, about 2 minutes. Blend in the parsley and lemon juice. Taste and add more mint, parsley, and lemon juice, if you wish. (I like the soup very lemony and use about 3 tablespoons for the pot-full, but this is a matter of taste.) Serve in large soup bowls.